/*
 * Copyright 2000-2016 JetBrains s.r.o.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.intellij.util.containers;

import org.jetbrains.annotations.NotNull;

import java.util.Collection;
import java.util.Iterator;
import java.util.NoSuchElementException;

public class SequenceIterator<T> implements Iterator<T> {
    private final Iterator<T>[] myIterators;
    private int myCurrentIndex;

    public SequenceIterator(@NotNull Iterator<T>... iterators) {
        //noinspection unchecked
        myIterators = new Iterator[iterators.length];
        System.arraycopy(iterators, 0, myIterators, 0, iterators.length);
    }

    public SequenceIterator(@NotNull Collection<Iterator<T>> iterators) {
        //noinspection unchecked
        this(iterators.toArray(new Iterator[0]));
    }

    @Override
    public boolean hasNext() {
        for (int index = myCurrentIndex; index < myIterators.length; index++) {
            Iterator iterator = myIterators[index];
            if (iterator != null && iterator.hasNext()) {
                myCurrentIndex = index;
                return true;
            }
        }
        return false;
    }

    @Override
    public T next() {
        if (hasNext()) {
            return myIterators[myCurrentIndex].next();
        }
        throw new NoSuchElementException("Iterator has no more elements");
    }

    @Override
    public void remove() {
        if (myCurrentIndex >= myIterators.length) {
            throw new IllegalStateException();
        }
        myIterators[myCurrentIndex].remove();
    }

    @NotNull
    public static <T> SequenceIterator<T> create(@NotNull Iterator<T> first, @NotNull Iterator<T> second) {
        return new SequenceIterator<T>(first, second);
    }

    @NotNull
    public static <T> SequenceIterator<T> create(@NotNull Iterator<T> first, @NotNull Iterator<T> second, @NotNull Iterator<T> third) {
        return new SequenceIterator<T>(first, second, third);
    }
}

